The present invention relates to a regenerative control device for a hybrid vehicle.
Among hybrid vehicles mounted with an engine and a traveling motor as driving sources of the vehicle, there is a vehicle in which a traveling motor generator where a power generation function is added to the traveling motor is used and a power generation motor generator is coupled to the engine separately from the traveling motor generator in such a manner that the driving power of the engine can be connected and disconnected to and from a power transmission path. That is, this is a series-parallel hybrid vehicle where the generation of the driving power and the power generation are performed separately at each of the engine and the traveling motor generator.
In the hybrid vehicle as described above, not only the power performance of the vehicle but also the energy efficiency during traveling are improved by using both the engine and the traveling motor generator.
For example, during traveling by the driving power of the traveling motor generator, the battery can be charged by the regenerative power generated during deceleration, and a regenerative braking power such as engine braking can be provided to the wheels. Further, the battery can also be efficiently charged by operating the engine at a rotation speed where the operation efficiency is high and driving the power generation motor generator by this engine.
On the other hand, in the hybrid vehicle as described above, since the frequency of battery charging during traveling is increased, there is a concern about battery overcharging. In particular, the amount of recovery of the regenerative power generated by the traveling motor generator affects the magnitude of the braking power of the vehicle. For this reason, it is desired to travel while recovering the regenerative power of the traveling motor generator by using some kind of method even when the battery is nearly fully charged.
Accordingly, a related art has been proposed where the motor generator coupled to the engine is driven as an electric motor to forcibly rotate the stopped engine (motoring). That is, the engine in a state of being separated from the power transmission path of the vehicle is used as the rotational load of the motor generator to cause the motor generator to consume power. By this control, regenerative braking can be performed while restricting the charging to the battery, so that driving feeling can be improved (see JP-A-2012-6525).
Moreover, a related art has been proposed where when the regenerative control of the traveling motor generator is performed with power generation while battery charging is restricted, in a case where a rotational resistance increase request to increase the rotational resistance of the engine is not made, driving of the power generation motor generator is controlled so that motoring of the engine is performed and in a case where the rotational resistance increase request is made, driving of the power generation motor generator is controlled so that the motoring of the engine is performed while the operation of the engine is controlled in such a manner that the valve timing is advanced compared with when the rotational resistance increase request is not made and that the throttle opening is adjusted within a range where the pressure of the intake system does not become lower than a predetermined pressure (see JP-A-2010-247749).
With this, even when the regenerative control of the traveling motor generator is performed while battery charging is restricted, the power generated by the traveling motor generator can be more reliably consumed by the motoring of the engine, and the lubricating oil can be inhibited from being sucked into the intake system and the combustion chamber of the engine because of the negative pressure of the intake system in association with the motoring of the engine.
On an exhaust pipe from the engine, a LAF (linear air-fuel ratio) sensor that detects the air-fuel ratio of the exhaust gas is placed. The LAF sensor is capable of detecting the ratio between air and fuel in the exhaust gas as a continuous value, and is wide in detection range and is high in accuracy, compared with an O2 sensor that has generally been used.
Here, when the engine is rotated by motoring as described above, the oil in the cylinder is discharged as it is in the direction of the exhaust pipe since combustion in the cylinder is not performed. By this oil adhering to the LAF sensor, the measurement accuracy of the LAF sensor decreases, so that the emission performance of the vehicle can decrease.